While the specific pathogenesis of periodontal disease is still unknown, attention has recently focused on several immunological mechanisms. One major objective of this proposed research is to learn more about the role of immediate hypersensitivity in gingivitis, periodontitis and acute necrotizing ulcerative gingivitis. An in vitro assay for immediate hypersensitivity will be applied to studying human periodontal disease. Oral microbial antigens and plaque sonicates will be incubated with peripheral leukocytes and gingival tissue to measure histamine release as a result of immediate hypersensitivity. The relative contributions of immediate hypersensitivity, delayed hypersensitivity and Arthus reactions to histamine release from challenged gingiva will be examined in monkeys. Immediate hypersensitivity as measured by histamine assays and delayed hypersensitivity as measured by lymphocyte transformation will be compared simultaneously. Leukocytes from patients with varying severities of periodontal disease will be challenged with plaque sonicates and they assayed by both methods. Patients with ANUG will be studied to see if their gingival bacteria are coated in vivo with complement and immunoglobulins. The potential role of immediate hypersensitivity and Arthus reactions will be considered in light of these results. A second major objective of this research is to examine the immunology of desquamative gingivitis. Biopsies and sera from patients with desquamative gingivitis will be studied by immunofluorescence for antibodies to gingiva. The incidence of cicatricial pemphigoid, bullous pemphigoid, pemphigus vulgaris and lichen planus which clinically manifest themselves as desquamative gingivitis will be examined. The potential value of immunofluorescence in the diagnosis of desquamative gingivitis will also be considered.